1. Field of the Invention
The invention relates in general to a display having a current driving circuit. More particularly, the invention relates to a display having an amorphous silicon thin-film transistor (α-Si TFT) current driving circuit.
2. Related Art of the Invention
The first dynamic image visible to human being includes the recorded movie. Later on, following the invention of cathode ray tube (CRT), the commercial television is developed, which has now become an inevitable appliance to every household. The further application as the desktop monitor for computer industry outlives the cathode ray tube for several decades. However, the radiation problems and the huge volume occupied by the internal electron gun adverse the trends of being thinner, lighter and large area display.
To resolve the above problems, flat panel displays have been developed. This field comprises liquid crystal displays (LCD), field emission display (FED), vacuum fluorescent display (VFD), organic light-emitting diode (OLDE) and plasma display panel (PDP).
The organic light-emitting diode is also referred as organic electroluminescence display, which is a self-luminescent dot-matrix display. The organic light-emitting device is driven by direct current (DC) voltage and has high intensity, high efficiency, high contrast ratio, and thin and light characteristics. Having theses characteristics and a high degree of freedom from three primary colors, that is, red (R), green (G) and blue (B), to white, the organic light-emitting diode is thus an important flat panel display technique to be developed in the next generation. In addition to the light, thin, and high-resolution properties of the liquid crystal display, the organic light-emitting diode further has the advantage of high speed and low-power cold light source. Other advantages such as wide viewing angle, effective color contrast, and low cost are also provided. The organic light-emitting diode can be applied to cellular phone, digital camera, personal data assistant, and the larger area display.
From the driver viewpoint, the organic light-emitting diode can be divided into a passive matrix driving type and an active matrix driving type. The passive matrix driving type is advantageous in its simple structure, of which the thin-film transistor (TFT) is not required. However, its drawback includes the inapplicability of obtaining high-resolution image quality. When the display is developed with a large area, the power consumption is increased, the lifetime is shortened, and the display performance is poor. Other the other hand, the active matrix type organic light-emitting diode has the active driving matrix applicable to large-size display. Further, the viewing angle is wide, the contrast is high, and the response speed is fast. However, the cost is slightly higher than the passive matrix driving type organic light-emitting diode.
For the active matrix driving type organic light-emitting diode, the pixels are typically driven by current. Currently, the current driving method of the active matrix organic light-emitting diode has to incorporate the production technique of low-temperature polysilicon (LTPS) thin-film transistor since which are mainly constructed by p-type or p-type and n-type thin-film transistors. The low-temperature polysilicon thin-film transistors have the characteristics of high mobility of electrons and holes and providing the p-channel; therefore, a driving current larger than that of the amorphous silicon thin-film transistor is provided. For the amorphous silicon, a proper p-channel thin-film transistor cannot be fabricated, so that the current driving method cannot be applied to the pixels thereof. Further, in the current-driving circuit, the driving current and data current are about the same, so that an driving integrated circuit (IC) is required to provide different data currents, so as to compensate the effects caused by different characteristics for the R, G and B pixels.